Got this extract over at mindandmuscle, it helps explain why DHT derived steroids such as Var help strength.

"It is important to understand that even though testosterone is the active androgen in muscle, and DHT exhibits relatively little direct anabolic effects on muscle in men, DHT is still very important for realizing the full performance-enhancing effects from testosterone. What I specifically mean here is DHT’s effects on the central nervous system, which lead to increased neurological efficiency (strength), and increased resistance to psychological and physical stress - not to mention optimal sexual function and libido.
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